This invention relates to an improvement of an electronic musical instrument of a time division multiplexed type, in which the keyboard of a single keyboard type electronic musical instrument is divided into a plurality of key ranges, different tone colors are employed for different key ranges, and the lowest (or highest) tone in a predetermined key range is generated with a different tone color.
There is a prior art electronic musical instrument in which single keyboard is divided into plural key ranges, and the lowest (or highest) tone in the predetermined key range is generated with a different tone color. This prior art electronic musical instrument is so designed that analog tone signals corresponding to individual key switches are selected by means of the switches, and a particular preference circuit is provided to select the lowest (or highest) tone. Accordingly, it is necessary to additionally provide key switches in correspondence to the preference circuit, beside the normally used key switches. Thus, the prior art electronic musical instrument is disadvantageous in that the number of key switches is increased, and, accordingly, the wiring between the key switches and the relevant electrical circuits becomes necessarily intricate. In addition, in the prior art electronic musical instrument, the analog tone signals are directly selected by the key switches, as was described above. Therefore, the technical concept of the prior art electronic musical instrument cannot be applied directly to a digital process type electronic musical instrument.
Accordingly, an object of this invention is to eliminate all of the above-described difficulties accompanying the prior art electronic musical instrument.
More specifically, an object of the invention is to provide an electronic musical instrument, in which, unlike the prior art electronic musical instrument, there are provided key switches for preferentially selecting the lowest tone (or highest tone) and ordinary key switches thereby including two key switch arrays, but instead merely by using one key switch array it is possible not only to ordinarily generate musical tones according to key operations but also to generate the lowest (or highest) tone with a different tone color.
It is another object of the invention to provide an electronic musical instrument in which no special key switch array is required for detecting the lowest or highest note, whereby key switch wirings can be saved and an integral circuit design can readily be introduced.
This invention can be effectively applied to an electronic musical instrument of a type in which key depression is detected in a key switch array to provide key depression data (which is representative of a key depressed), and according to the key depression data musical tone signals are produced. A process for key range division is carried out by using digital key depression data obtained from a key depression detection circuit called "a key coder" or "a key code data generating unit". The purpose of the "key range division" is that, as was described before, a single keyboard is divided into a plurality of key ranges, and tones in different key ranges are produced with different tone colors, as if an electronic musical instrument having a plurality of keyboards were played. The key ranges have tone generators, respectively, and the tone generators of the key ranges can carry out their own tone color formation. Therefore, it is possible to provide different tone colors for different key ranges. In the process for key range division, a key range to which a key concerning key depression data belongs is discriminated, so that the key depression data is effectively used in the tone generator of the key range.
In this invention, with respect to a predetermined key range tones of the depressed keys, in the key range are generated with a common tone color by the tone generator of that key range, and the lowest (or highest) key depression tone is generated with a tone color different from the common tone color. The merit of this is that, besides the effect of the key range division, an effect obtainable from provision of an additional keyboard for monophonic performance is produced. It can be readily understood that the key depression data of the lowest (or highest) tone in the key range is utilized in both the tone generator of the key range and the tone generator for the monophonic performance. For this purpose, in the prior art electronic musical instrument, two key switch arrays, i.e., the ordinary key switch array and the key switch array for preferencially selecting the lowest (or highest) tone are provided. This point is improved according to the invention. That is, one of the specific features of the invention resides in that, among time slots allotted for key depression data delivered out in succession according to the detection scanning of one key switch array, a time slot for the key depression data of the lowest (or highest) tone in the predetermined key range is divided into two portions, i.e. a first half and a second half, and during the first (or second) half of the time slot, the key depression data is processed for forming a musical tones with a common tone color in the key range, whereas during the second (or first) half the key depression data is processed for forming a musical tone with a tone color different from the common tone color.
It is considerably effective for the detection of the lowest (or highest) tone to carry out the scanning of the key switch array in the order of increasing (or decreasing) tone pitches. If this method is employed, key depression data delivered out first in one scanning cycle can be regarded automatically as that of the lowest (or highest) tone. Therefore, it is unnecessary to provide an intricate circuit such as the lowest (or highest) tone detection circuit; that is, the lowest (or highest) tone can be detected by using a simple circuit (such as a circuit for detecting the rise of a digital signal).